Isolation and Characterisation of Anti-plasmodial Compounds from Selected Medicinal Plants from South Nyanza Region

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Abstract

Malariacaused by Plasmodium parasites, still has an overwhelming impact on public
health in developing nations. Due to its prevalence, virulence and drug resistance, it
remainsone of the most serious and widespread parasitic disease in sub-Saharan Africa.
The fight against malaria has been hampered by inadequate drug supply, high costs of
drugsandlack of an effective vaccine. Consequently there is need for continued research
on the discovery and development of new more efficacious anti-malarial drugs. In this
work, bio-evaluation of three Kenyan medicinal plants used in treatment of malaria in
westernKenya:Clerodendrum myricoides (Oliv.), Clerodendrum rotundifolia (Hochst.),
and Hypoestesforskolei (Vahl.), was undertaken. The root extracts were sequentially
extractedstarting with hexane, DCM, EtOAc and MeOH. Isolation of compounds was
doneby column,preparative and thin layer chromatography. Identification of compounds
was done by IH NMR, COSY, I3C NMR, DEPT, HMBC, IR, mass spectroscopy and
comparisonwith published data. Preliminary activity and cytotoxicity studies were done
on vero cells 199. Extracts were screened against Plasmodium falciparum chloroquine
sensitivestrain (D6) and the following results noted: C. myricoides (hexane 8.72±1.81,
DCM IOl±1.56, EtOAc <3.91 and MeOH 19.73 ug/ml.), C. rotundifolia (hexane
4.65±O.64,DCM 9.6l±O.lI, EtOAc 5.81±0.47 and MeOH 8.06±O.35 ug/ml.) and H.
forskolei (hexane 14.l2±3.75, DCM 4.00±1.25, EtOAc 20.l0±14.03 and MeOH
4.92±0.44 ug/ml.). Hypoetesforskolei DCM extract yielded 3,4a,7,7,10a-pentamethyl-3-
vinyl dodeca hydrobenzo [f] chromene(93) and 3,4a,7,7,10a-pentamethyl-3-vinyl dodeca
hydrobenzo [f] chromen-Bsol (94) and kaur-16-ene-19-oic acid (95); Clerodendrum
myricoidesEtOAc fraction afforded stigmasterol (89), lupeol (90), and p-hydroxy benzyl
octaeicosanoate (91) while Clerodendrum rotundifolia DCMlEtOAc fractions realized
oleanolicacid (92). p-hydroxyhe~l octaeicosanoate (91) is being reported for the first
time from Clerodendrum myricoides, while, 3,4a,7,7,10a-pentamethyl-3-vinyl dodeca
hydrobenzo[f]chromene(93) and 3,4a,7, 7,1Oa-pentamethyl-3-vinyl dodeca hydrobenzo
[f]chromen-8-01(94) and kaur-16-ene-19-oic acid (95) are also reported for the first time
from Hypoetes forskolei. The isolated compounds exhibited mild to moderate antiplasmodial
activity against chloroquine sensitive Plasmodium falciparum strain (D6).
The results obtained form a good basis for further investigation of the isolated
compounds for possible synergism and structure activity studies to improve their antiplasmodial
activity. The isolated compounds can be good leads for development into
anti-malarial compounds.There is need therefore to preserve the plants as well as the
.extractedcompounds for further structure-activity studies